Issue reported by Umbire: if hero dies by drowning on the Plane
of Water, cause of death was reported as "drowning in a limitless
water".
Reported for livelogging but applied to tombstone and logfile too.
Omit the article "a" in this situation.
For 3.6.7, it would have started as "drowning in a water" and been
updated on the fly to be "drowning in deep water". 3.7 changed
terrain type WATER to be "wall of water", where "a" is expected,
and also added "limitless water" for Plane of Water, but it was
neglecting to include a similar fixup for the latter. The "deep
water" fixup is still present but doesn't get triggered anymore.
Fixes#1248
5641e2560f